Granitic Rock Samples Research Articles

Numerical analysis on scale effect of elasticity, strength and failure patterns of jointed rock masses

It is of great importance to study the failure process and scale effect of jointed rock mass in the field of rock mechanics and mining engineering. In the present paper, initially the uniaxial compression test on granite was performed and acoustic emission (AE) sequence was acquired during the compression process in laboratory. Results from numerical simulations using the particle flow code in two dimensions (PFC2D) were presented, and compared with experimental measurements. It was observed that the approach was reasonably good in predicting the real response of granite rock samples. The mechanical parameter of joint model was then calibrated based on PFC2D model with experimental results. Finally the mechanical properties of complex rocks with discrete fracture network (DFN) were studied and scale effects on the elasticity and strength were then investigated. The result showed that the failure pattern was similar when the ratio of joint contact bond strength (both shear and normal) to rock contact bond strength was in the range of 3~9%. The elastic modulus and strength parameters were changed with the sizes of rock sample for DFN models. Moreover, the variation of rock failure pattern under different sizes was also studied and finally the representative elementary volume (REV) size of the considered rock mass was estimated to be 9 × 9 m. It is suggested that the failure pattern analysis should be considered in the REV study of jointed rock mass.

Minimal required boundary conditions for the thermal spallation process of granitic rocks

The spallation process is based on the effect, that hard rocks with a high quartz content disintegrate into small disc-like fragments, if the rock surface is rapidly exposed to high thermal loads. Spallation is pursued as a contact-free drilling technology for various applications. In view of increasing the knowledge about the process and for determining the limitations of the applicable operating range, a profound knowledge of the minimal required boundary conditions are of significant importance. These conditions are characterized by the lowest surface temperature and heat transfer coefficient at which spallation can be successfully initiated. In order to determine the minimal required boundary conditions, spallation experiments were conducted in which granitic rock samples were rapidly heated by a methane–air burner. A novel measuring concept is proposed to measure the surface temperature, using high-speed pyrometers to temporally resolve the detachment of single spalls. The heat transfer coefficient of the impinging flame was determined by measuring the heat flux in the stagnation point of the jet using an industrial heat flux sensor. The reported data of the boundary conditions show good accordance with data published by other researches and supports their proposed characteristic for the specific heating process.

Assumptions of the analytical solution for solute transport in a fracture–matrix system

This study focuses on numerical modeling of fluid flow and solute transport in rough-walled rock fractures and fracture-matrix systems, with the main aim to investigate the impacts of fracture surface roughness on flow and transport processes in rock fractures. Both 2D and 3D fracture models were built from laser-scanned surface tomography of a real granite rock sample, to consider realistic features of surface tomography and potential asperity contacts. The flow was simulated by directly solving the Navier-Stokes equations (NSE) and the transport was modeled by solving the advection-dispersion equation (ADE) in the entire domain of fracture-matrix system, including matrix diffusion process. Such direct simulations provided detailed flow and concentration fields for quantitatively analysis of flow and transport behavior. The detailed analysis of surface roughness decomposition, complex flow patterns (i.e., channeling, transverse and eddy flows), effective advective flow apertures, effective transmissivity, effective dispersivity, residence time, transport resistance and specific surface area demonstrated significant impacts of realistic fracture surface roughness on fluid flow and solute transport processes in rock fractures. The results show that the surface roughness and shear displacement caused asperity contacts significantly enhance nonlinearity and complexity of flow and transport processes in rough-walled fractures and fracture-matrix systems. The surface roughness also causes invasion flows in intersected fractures which enhance solute mixing at fracture intersections. Therefore, the fracture surface roughness is an important source of uncertainty in application of such simplified models like cubic law (CL) for fluid flow and analytical solutions for solute transport in rock fractures. The research conducted advances our understanding of realistic flow and transport processes in natural fractured rocks. The results are useful for model validation/extension, uncertainty analysis/quantification and laboratory experiments design in the context of various applications related to fracture flow and transport.

Determination of uranium concentrations and 234U/238U activity ratio in some granitic rock samples by alpha spectrometry: Application of a radiochemical procedure

The present study is an application of a radiochemical procedure using alpha spectrometry technique for determination of uranium isotopes 238 U,234 U, and 235 U on 13 granitic samples. These samples were collected from Gabal Gattar area, Northeastern Desert, Egypt. The collected samples were digested using microwave technique with aqua regia and spiked with 232 U for chemical yield and activity calculation. Separation of uranium isotopes from the samples was done by Dowex 1 × 4 (50–100 mesh) resin followed by source preparation using microprecipitation technique. The concentrations of 238 U were ranged between 28.9 ± 0.9 and 134.8 ± 1.8 Bq/g, and the 234 U concentrations were between 24 ± 0.6 and 147.7 ± 2.2 Bq/g. For the 235 U, the activity concentrations were between 1.3 ± 0.2 and 6.7 ± 1.2 Bq/g. The activity ratio of 234 U/238 U was calculated and varied from 0.80 to 1.30.

A radiological survey of the Eğrigöz granitoid, Western Anatolia/Turkey.

A radiological survey of the granitoid areas throughout Western Anatolia was conducted during 2007-14. As a part of this radiological survey, this article presents results obtained from Eğrigöz pluton, which lies in the northeastern region of Western Anatolia. In the investigated area, the activity measurements of the natural gamma-emitting radionuclides ((226)Ra, (232)Th and (40)K) in the granitic rock samples and soils have been carried out by means of the NaI(Tl) gamma-ray spectrometry system. The activity concentrations of the relevant natural radionuclides in the granite samples appeared in the ranges as follows: (226)Ra, 28-95 Bq kg(-1); (232)Th, 50-122 Bq kg(-1) and (40)K, 782-1365 Bq kg(-1), while the typical ranges of the (226)Ra, (232)Th and (40)K activities in the soil samples were found to be 7-184, 11-174 and 149-1622 Bq kg(-1), respectively. Based on the available data, the radiation hazard parameters associated with the surveyed rocks/soils are calculated. The corresponding absorbed dose rates in air from all those radionuclides were always much lower than 200 nGy h(-1) and did not exceed the typical range of worldwide average values noted in the UNSCEAR (2000) report. Furthermore, the data are also used for the mapping of the surface soil activity of natural radionuclides and the corresponding gamma dose rates of the surveyed area.

Geochemistry, zircon U–Pb geochronology and Hf isotopes of granitic rocks in the Xitieshan area, North Qaidam, Northwest China: Implications for Neoproterozoic geodynamic evolutions of North Qaidam

Neoproterozoic granitic rocks in the Dakendaban Group are widely distributed throughout the Xitieshan area as the old basement in North Qaidam, NW China. The granitic rocks are composed predominantly of K-feldspar, plagioclase, quartz, muscovite and biotite, with subordinate zircon, garnet, titanite and sillimanite. Two granitic rock samples yielded ages of 930±6Ma and 918±6Ma using LA-ICPMS zircon U–Pb dating, which are interpreted as the protolith formation age of the granitic rocks, and reflecting an important Neoproterozoic magmatic event in the Xitieshan area.Geochemical data suggest that the granitic rocks are characterized by high SiO2, K2O, and CaO/Na2O ratios (0.48–1.04), with LREE enrichment and strong Eu negative anomalies (Eu/Eu*=0.44–0.51), and negative anomalies of Nb, Ta, Ti, Zr, and Hf. These rocks have consistent Nd isotope compositions with ɛNd(t) values ranging from −4.83 to −4.27, while the sample 2011ZJ18-3 yielded the negative ɛHf(t) values ranging from −6.7 to −1.3, and tDM2(Hf) model ages ranging from 1.9 to 2.2Ga. These geochemical and zircon Lu–Hf isotopic features suggest that the granitic rocks in the Xitieshan area belong to the S-type granite, which were mainly derived from the partial melting of the Paleoproterozoic continental crust material (1.9–2.2Ga) that were predominantly composed of metagreywackes and subordinate metapelitic sources. Based on the regional tectonic reconstruction, we propose that the studied rocks occurred as syn-orogeny on an active continental margin in a compressional environment, which resulted from the Neoproterozoic arc-continent collision and subsequently continent–continent collision, leading to the significant continental growth. The Early Neoproterozoic tectonothermal event in North Qaidam shares many affinities with that of the Tarim block and South China block (Yangtze block) that were associated with the final consolidation of block at the Jinning orogeny, showing an agreement with the formation of Rodinia. The Early Neoproterozoic S-type granitic magmatism in NW China, including the Qaidam and adjacent blocks, is an important episode of continental crust reworking.

New weathering indices for evaluating durability and weathering characterization of crystalline rock material: A case study from NE Turkey

There are several methods to characterize petrochemical properties of crystalline rocks. One method is based on the ionic model. In the model, large oxygen atoms of the rock-forming minerals are close-packed framework structures. The distribution of cations, which is defined by the “Cation-Packing Index” or the k-value for each (stoichiometric) mineral phase, can be correlated with the petrophysical properties. These properties, representing the engineering behavior of the rock materials show a dependence on the physical and chemical changes due to weathering. The fundamental systems of the chemical weathering of rocks are the leaching of the alkaline and alkali-earth elements and the redistribution of the residual elements into secondary minerals. In this study, these conditions are considered as the basis for new petro-chemical weathering indices based on the cation-packing value for evaluating weathering characterization of crystalline rocks. These indices are the k-product index, the k-leaching index and the k-weathering index. The k-product index represents the quantity of the weathering product suggested in this study, whereas the k-leaching index represents the amount of chemical leaching during the weathering. The k-weathering index was defined as the sum of the k-leaching index and the k-product index. In addition to these new engineering indices, a k-durability index based on a slake durability index and the k-value of the rock materials was suggested in this study to estimate the durability and the mechanical properties of rock materials. These indices were applied to granitic rock samples weathered to various degrees, from the Kurtun Granodiorite in northeastern Turkey. The results of the regression analysis performed in this study show that the k-weathering index can be used as a weathering indicator and that the k-durability index can be used to evaluate the durability and the mechanical behaviors of the investigated samples. It would be useful to conduct further research to confirm the results of the present study.

Rare earth elements determination and distribution patterns in granite rock samples by using INAA absolute method

This work determined elemental concentrations for rare earth elements (REE) in granite rock samples using the INAA absolute method. The accuracy of INAA absolute method was determined by analyzing two of USGS STM-1 and MAG-1 standards. The analytical results agreed reasonably well with certified values. In general, all analytical results had Z score less than 1.0 excepting Yb. The REE found in granite rock samples ranged from 116 to 325 mg kg−1. The total content of REE in granite rock samples was 206 mg kg−1. Patterns for REE were also studied in the present work.

Stepwise extraction of Th(IV) and U(VI) ions with mixed-ligands impregnated resin containing 1,4-diaminoanthraquinone and 1,4-dihydroxyanthraquinone

A new solvent impregnated resin (SIR) was prepared using Amberlite XAD-16 in contact with 1:1 mixed-ligands of 1, 4-diaminoanthraquinone and 1, 4-dihydroxyanthraquinone. The SIR showed appropriate selectivity toward U(VI) and Th(IV) ions when packed in the columns at pH 6.5 and 5, respectively. U(VI) and Th(IV) ions were then easily separated through the elution by 2 and 4 M HCl with the detection limits of 1 × 10−9 and 2 × 10−9 M, respectively. The recoveries for the spiked amounts of these ions to the granite rock and natural water samples were >95 %, which confirmed applicability of the proposed method.

Structural map of Variscan northern Sardinia (Italy)

In this paper, we present a geological structural map (1:100,000 scale, ∼2300 km2 surface area) of the Variscan basement of northern Sardinia. The map integrates field structural analysis, extensive gamma-ray spectrometry, and high-resolution ELA-ICP-MS U/Th-Pb zircon and monazite dating. A set of 10 samples of granitic rocks collected from different plutons were characterized for their crystallization age. This provided an accurate timing of magmatic events related to the development of the Corsica-Sardinia Batholith. The structural map, complemented with geochronological results represents a benchmark for future studies on Variscan geodynamics.

Evaluation of drilling efficiency by percussion testing of a drill bit with new button arrangement

Rock drilling machines are commonly used for surface drilling, soil nailing reinforcement, tunnel excavation, and underground mining. These machines use drill bits that directly impact into the rock and are operated by percussive force and torque. Drill-bit buttons need to be designed to increase drilling efficiency; here, we present the results of a series of single blow tests on granitic rock samples using a piston drop type percussion testing system that enable us to compare the drilling efficiency of a new button arrangement design with conventional arrangements. Drilled rock volumes were measured by laser scanner after testing, and drilling efficiencies were evaluated by calculating percussive energies and drilled volumes. The results indicate that the new button arrangement design can be used to improve the drilling efficiency.

Natural radioactivity concentrations in Alvand granitic rocks in Hamadan, Iran

Natural radioactivity of 30 granite rock samples collected from Alvand plutonic complex was determined using a high-resolution, high purity germanium gamma-spectrometry system. The activity concentrations of 226 Ra, 232 Th and 40 K varied from 8.4 ± 0.6 to 119.3 ± 1.9, i.e., minimum detectable activities (MDA) to 268.4 ± 3.3 and 62.9 ± 4.1 to 1602.6 ± 27.9 Bq/kg, respectively. 137 Cs ranged from MDA to 4.9 ± 0.7 Bq/kg. The radium equivalent activity varies between 35.7 and 624.2 Bq/kg that is lower than the permitted value (370 Bq/kg) except in three samples. The absorbed dose rate ranged from 17.9 to 282.8 nGy/h, and the effective dose rate outdoor was determined to be between 21.9 and 347.0 μSv/y. The annual effective dose rate indoor varied from 87.8 to 1388.2 μSv/y that is lower than the dose criterion, 1 mSv/y, except for PGG(W) and GRG(W) samples. The internal and external hazard indices values range from 0.1-2.0 to 0.1-1.7, respectively, only four out of 30 showed values higher than unity.

Investigate the capability of INAA absolute method to determine the concentrations of 238U and 232Th in rock samples

This work aimed to study the capability of INAA absolute method in determining the elemental concentration of 238U and 232Th in the rock samples. The INAA absolute method was implemented in PUSPATI TRIGA Mark II research reactor, Malaysian Nuclear Agency (NM). The accuracy of INAA absolute method was performed by analyzing the IAEA certified reference material (CRM) Soil-7. The analytical results showed the deviations between experimental and certified values were mostly less than 10 % with Z-score in most cases less than 1. In general, the results of analysed CRM Soil-7 show a good agreement between certified and experimental results which mean that the INAA absolute method can be used accurately for elemental analysis of uranium and thorium in various types of samples. The concentration of 238U and 232Th ranged from 1.77 to 24.25 and 0.88 to 95.50 ppm respectively. The highest value of 238U and 232Th was recorded for granite rock sample G17 of 238U and sample G9 of 232Th, whereas the lower value was 1.77 ppm of 238U recorded in sandstone rock and 0.88 ppm of 232Th for gabbro. Moreover, a comparison of the 238U and 232Th results obtained by the INAA absolute method shows an acceptable level of consistency with those obtained by the INAA relative method.

Evaluating the effect of radio-frequency pre-treatment on granite rock samples for comminution purposes

The international mining industry needs to enhance its mineral liberation process and reduce its enormous amount of power consumption, thereby increasing its overall efficiency. Current research studies have found that the mineral liberation process can be enhanced through the use of pulsed power, ultrasound pre-treatment and microwave pre-treatment of run of mine ore. The purpose of this article is to present empirical results of treating specific granite rock samples with RF power within the VHF range. These results indicate that RF treatment of granite rock samples within the VHF range does not significantly weaken the mineral grain boundaries. These results prove that RF pre-treatment of these rock samples will not benefit the mineral liberation process. However, different results may be obtained from samples that contain mineral species that are more absorbent of electromagnetic radiation.

인공풍화과정에 의한 김해지역 백악기 화강암의 풍화특성에 관한 연구

암석에 대한 풍화특성 연구는 시공간적 제약으로 인한 어려움이 따른다. 이 연구는 경상남도 김해시 일대에 분포하는 백악기 화강암에 대하여 물리적 및 화학적 풍화과정을 인공적으로 재현하고 풍화진행에 따른 암석의 지질공학적 특성변화를 고찰하였다. 인공풍화과정에 의하여 시료의 탄성파속도는 현저하게 감소하였으며 공극률 및 흡수율은 뚜렷하게 증가하였다. 초기 풍화등급이 높은 암석일수록 인공풍화과정에 따른 물성변화의 폭이 크며 풍화에 취약한 것으로 나타났다. 공극률, 흡수율 및 탄성파속도는 연구지역의 화강암에 대한 풍화지수로 유용하게 사용할 수 있다. 물리적 및 화학적 풍화과정이 복합적으로 일어나는 조건에서 암석풍화는 더욱 촉진된다. 이 연구에서 복합적인 풍화과정을 재현한 연구방법은 암석의 풍화특성을 규명하고 예측하는 데에 활용할 수 있을 것으로 기대된다. It is very difficult to capture the weathering characteristics of rock because of limitation caused by time and space. A new scheme of experiment that includes physical and chemical weathering processes was implemented on Cretaceous granitic rock samples from Kimhae area to investigate the variations of geomechanical properties of deteriorated rocks due to artificial weathering processes. The seismic velocity was found to decrease with increasing artificial weathering cycle. Effective porosity and absorption tend to increase with artificial weathering processes. The amount of deterioration of rock samples depend on pre-test degree of weathering. Effective porosity, absorption and seismic velocity can be used as the measure of weathering characteristics of granite in the study area. Weathering is accelerated by combined effect of physical and chemical weathering processes. The new experimental methodology conducted in this study has strong capability to analyze the weathering characteristics of rocks.

Structural Modification of Chalcopyrite Ore for Enhanced Copper Recovery

Malanjkhand copper project, Madhya Pradesh, India, generates a lot of lean sulphidic ores containing chalcopyrite (³0.3% of copper) with traces of oxidized, semi-oxidized and secondary sulfides. EPMA analysis shows that the granitic rock samples have plagioclase feldspar, orthoclase feldspar and quartz as major constituents within which the ore minerals are sparsely distributed. Due to the complex structure and low solubility of the sulphide-bearing granitic rock, the dissolution of copper from the hard matrix is difficult. The present study deals with change in crystallographic and chemical nature of the mineral system present in the host rock. In an attempt to increase copper recovery, the ore was subjected to heating at 600°C under normal atmospheric conditions. This heat treatment resulted in enhanced copper recovery, up to 98% within 60 days of progressive leaching. [doi:10.2320/matertrans.M2012128]

Numerical simulation of stress wave induced fractures in rock

Blast-induced fracture networks largely control the degree of rock fragmentation and final outcome of blasting operations. Precise laboratory-scale single-hole blast experiments have been carried out in cylindrical samples of a well-characterized granitic rock to study stress wave induced fracture patterns. The rock samples measured 144 mm in diameter and 150 mm in length. Detonating cord was employed as the explosive source in the centrally loaded boreholes in the rock samples. In this paper, the measured mechanical properties, experienced peak pressure values inside the rock samples and blast-induced fracture patterns are used to find the parameters of Johnson-Holmquist model in ANSYS AUTODYN. The resulting numerical fracture patterns are comparable to those obtained from experiments at macro-scale level.

The ammonium content in the Malayer igneous and metamorphic rocks (Sanandaj-Sirjan Zone, Western Iran)

The ammonium content in the Malayer igneous and metamorphic rocks (Sanandaj-Sirjan Zone, Western Iran)The ammonium (NH4+) contents of the Malayer area (Western Iran) have been determined by using the colorimetric method on 26 samples from igneous and metamorphic rocks. This is the first analysis of the ammonium contents of Iranian metamorphic and igneous rocks. The average ammonium content of metamorphic rocks decreases from low-grade to high-grade metamorphic rocks (in ppm): slate 580, phyllite 515, andalusite schist 242. In the case of igneous rocks, it decreases from felsic to mafic igneous types (in ppm): granites 39, monzonite 20, diorite 17, gabbro 10. Altered granitic rocks show enrichment in NH4+(mean 61 ppm). The high concentration of ammonium in Malayer granites may indicate metasedimentary rocks as protoliths rather than meta-igneous rocks. These granitic rocks (S-types) have high K-bearing rock-forming minerals such as biotite, muscovite and K-feldspar which their potassium could substitute with ammonium. In addition, the high ammonium content of metasediments is probably due to inheritance of nitrogen from organic matter in the original sediments. The hydrothermally altered samples of granitic rocks show highly enrichment of ammonium suggesting external sources which intruded additional content by either interaction with metasedimentary country rocks or meteoritic solutions.

Time frame of 753–680 Ma juvenile accretion during the São Gabriel orogeny, southern Brazilian Shield

The time frame of the three main geological events in the Neoproterozoic Cambaí Complex, juvenile São Gabriel belt in the southern Brazilian Shield is established by integrating field mapping, back-scattered electron imaging and sensitive high-resolution ion microprobe (SHRIMP II) U–Pb dating of 96 zircon crystals from nine granitic and metasedimentary rock samples. The three events are: (1) voluminous flat-lying paragneisses (Cambaizinho Complex) and orthogneisses (Vila Nova gneisses) between 735 and 718 Ma, (2) tonalite–trondhjemite association (Lagoa da Meia-Lua Suite) between 710 and 690 Ma, and (3) late granodiorite intrusions (Sanga do Jobim Suite) at 680 Ma. An additional older volcanic event (Campestre Formation) was dated at 753 Ma. These results are most significant for the reconstruction of West Gondwana.

Influence of some rock strength properties on jaw crusher performance in granite quarry

The influence of rock strength properties on Jaw Crusher performance was carried out to determine the effect of rock strength on crushing time and grain size distribution of the rocks. Investigation was conducted on four different rock samples namely marble, dolomite, limestone and granite which were representatively selected from fragmented lumps in quarries. Unconfined compressive strength and Point load tests were carried out on each rock sample as well as crushing time and size analysis. The results of the strength parameters of each sample were correlated with the crushing time and the grain size distribution of the rock types. The results of the strength tests show that granite has the highest mean value of 101.67 MPa for Unconfined Compressive Strength (UCS) test, 6.43 MPa for Point Load test while dolomite has the least mean value of 30.56 MPa for UCS test and 0.95 MPa for Point Load test. According to the International Society for Rock Mechanic (ISRM) standard, the granite rock sample may be classified as having very high strength and dolomite rock sample, low strength. Also, the granite rock has the highest crushing time (21.0 s) and dolomite rock has the least value (5.0 s). Based on the results of the investigation, it was found out that there is a great influence of strength properties on crushing time of rock types.